Seasonality of feral horse grazing and invasion of Pinus halepensis in grasslands of the Austral Pampean Mountains (Arge

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ORIGINAL PAPER

Seasonality of feral horse grazing and invasion of Pinus halepensis in grasslands of the Austral Pampean Mountains (Argentina): management considerations Ana E. de Villalobos . Leonela Schwerdt

Received: 22 June 2019 / Accepted: 19 June 2020 Ó Springer Nature Switzerland AG 2020

Abstract The introduction of domestic ungulates has altered the natural grazing regime, promoting the invasion of exotic woody plants being seasonality or stoking season one of the key factors regulating the grazing regime. The Pampean Mountain grasslands of Central Argentina have been intensively transformed by the presence of feral horse populations that have increased the last 40 years, coinciding with an increased abundance of Pinus halepensis dispersed from cultivated stands. In this study, we evaluated the effect of the seasonal variation in perennial grasses defoliation (no defoliation; continuous defoliation; defoliation during autumn-winter and defoliation during spring-summer) on the establishment of P. halepensis seedlings and the response of the dominant perennial grasses (Nasella tenuis and Piptochaetium lejopodum) to defoliation in areas with different grazing histories, following a split-plot design. The establishment of P. halepensis was highest in the grazed areas and in treatments where the defoliation of the perennial grasses was practiced throughout the

year or during autumn-winter. Perennial grasses respond differently to defoliation according to the grazing history. In the grazed areas, defoliation negatively affected the perennial grasses during all the study period, showing the scarce resilience after grazing while in ungrazed areas, the perennial grasses were little affected by the seasonality of defoliation. Both, above- and belowground competition affected the establishment of P. halepensis, according to defoliation treatment and grazing history. The information obtained allows the elaboration of management recommendations to avoid the propagation of P. halepensis; therefore, the seasonal management of the grazing is a recommended practice toprevent or reduce the intensity of feral horse grazing during the autumn and winter months. Keywords Pines invasions  Feral horses  Grazing management  Natural grasslands

Introduction A. E. de Villalobos (&)  L. Schwerdt Grupo de Investigacio´n en Ecosistemas de Pastizal (GIEP), CERZOS, CONICET, 8000 Bahı´a Blanca, Argentina e-mail: [email protected] A. E. de Villalobos Departamento de Biologı´a Bioquı´mica y Farmacia, Universidad Nacional del Sur, 8000 Bahı´a Blanca, Argentina

The invasion of exotic woody plants has been recorded in the natural grasslands of South America (Chaneton et al. 2004; Chaneton et al. 2012), North America (Van Auken 2000; Lett and Knapp 2005), Australia (Pawson et al. 2010), Africa (Belayneh and Tessema 2017), Europe (Seastedt and Pysek 2011) and Asia (Khuroo et al. 2012). The invasions threaten native

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A. E. de Villalobos, L. Schwerdt

biodiversity, alter ecosystem fun